Two-step triangular phase-shifting is a recently developed method for 3-D shape measurement. In this method, two triangular gray-level-coded patterns, which are phase-shifted by half of the pitch, are needed to reconstruct the 3-D object. The measurement accuracy is limited by gamma non-linearity and defocus of the projector and camera. This paper presents a repeated phase-offset two-step triangular-pattern phase-shifting method used to decrease the measurement error caused by the gamma non-linearity and defocus in the previously developed two-step triangularpattern phase-shifting 3-D object measurement method. Experimental analysis indicated that a sensitivity threshold based on the gamma non-linearity curve should be used as the minimum intensity of the computer-generated pattern input to the projector to reduce measurement error. In the repeated phase-offset method, two-step triangular phaseshifting is repeated with an initial phase offset of one-eighth of the pitch, and the two obtained 3-D object height distributions are averaged to generate the final 3-D object-height distribution. Experimental results demonstrated that the repeated phase-offset measurement method substantially decreased measurement error compared to the two-step triangular phase-shifting method.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.